Paints are known to comprise suspension of one or more colouring constituents in a liquid-forming binder capable of converting to a solid film when a thin layer of it is applied to a metal, wood, stone, paper, or other surface and produces a continuous coloured film. The surface becomes coloured because it absorbs light of certain wavelengths. Many film-forming materials are used both as clear coatings and as pigment/binders mixtures. In case of solution vehicles,the binder is dissolved in a solvent to form a clear, viscous solution, and the pigment or the oxide is dispersed directly into the vehicle solution. On film formation the solidified vehicle serves to bind the pigment, forming a continuous film phase. Vehicles which belong to this category include drying oils, varnishes, synthetic resins and high polymeric materials such as the cellulosic and vinyl polymers.
In another type of vehicle the resins are dispersed in a liquid. Dispersion resins are in the form of tiny, spherical, insoluble particles suspended in a volatile liquid such as water or any volatile solvent. When the liquid evaporates, discrete particles of pigment, oxide or resin remain as a continuous film. Examples of dispersion coatings include the polyvinyl chloride organosols and synthetic rubber latexes.
Paints are normally prepared by mill-base mixing, followed by grinding, then let-down step and final mixing. Modern paints are "tailor-made" coatings which are usually designed by skilled scientists for specific purposes. Thus, there are known various types of paints, such as paints against corrosion, insulating paints which withstand at high temperatures, paints for electric conductance, etc. An important constituent in the paint dispersion is the binder which imparts the film forming properties. Some of the constituents possess different optical functions and are selected according to their spectral properties.
Almost all the paints on the market, comprise pigments and fillers which should fulfill the optical requirements at visible light, i.e. an electromagnetic radiation with a wavelength in the range of 0.4-0.7 micrometers. The three main constituents of the paints are:
(a) Pigments having the function to give the paint the opacity, colour and added durability, by protecting the oil and resin film from ultraviolet light. PA1 (b) Binders, which impart film forming properties. PA1 (c) Fillers, also known as matting reagents which have the property to aid in protecting the paint from weathering of the dyes and also to reduce the gloss of a paint. PA1 filler particles which satisfy the following:
When an electro-magnetic radiation hits a certain surface a part of it is reflected and the other part is refracted inside to the subsequent layer, being transmitted or absorbed. The reflected radiation comprises two main components: specular radiation and diffusive radiation. The specular surfaces possess a mirror-like appearance being obtained by volatilization of thin metals particles on a polished substrate.
There are cases when it is most desirable that the layer of the film resulted from a binder, should possess a low gloss property, which is generally achieved by adding a filler material such as, calcium carbonate, silicate, colloidal silica, etc. These compounds are actually used in most of the cases where no particular requirements on their absorption in the infra-red region is imposed. However, in case of films produced by paints which possess a high reflectance in the thermal infra-red range of 3 to 12 micrometers, these materials are not suitable. There are known paints useful for high reflective means which provide colour in the visible range and high reflectivity in the range of 3 to 14 micrometers, comprising paints with a high reflectivity and a suitable carrier, selected from thermosetting or thermoplastic compounds such as: epoxy, acrylic, silicone, polyvinyl chloride, etc.
According to the U.S. Pat. No.3,001,993 (Kapalko et al) polyethylene particles are used in a resinuous composition, in an mount of between 0.1% to 25% by weight of the composition, to eliminate sagging and sol vent popping present therein. The patent does not deal at all with the problem of reflectivity in the infra-red region. In this patent, there is a copolymerization, i.e. a chemical reaction between the constituents present in the composition i.e. polyethylene and acrylamide.
In the U.S. Pat. No. 4,916,014 (Weber et al) there are described infra-red reflecting paint compositions possessing improved visible transparency, known in the paint trade as "pearlescent". The compositions comprise: small particles of a substrate, a layer of an infra-red reflecting metal coated on the substrate and a layer of a dielectric material coated on the metal. The substrate can be selected from fine particles of mica glass, non-infra-red absorbing silicates and high molecular weight of solid hydrocarbons or a plastic material such as polymethacrylate and polyethylene terephthalate. These materials serve as an inert substrate which holds the infra-red reflecting layers. After its application, the binder constitutes a uniform continuous layer, without reflection and gloss properties. In this manner, the substrate material is completely coated and does not contribute to the spherical properties of the composition. The infra-red reflecting properties are obtained by the metallic layer and the dielectric layer.
In the U.S. Pat. No. 4,640,851 (Pusch) it is described a camouflage screen possessing a wide-band effect ranging from the visual part of the spectrum to the radar region. The material used comprises a base layer, an intermediate homogeneous metal layer and an outer camouflage paint layer, which consists of a binder transparent in the thermal infra-red range. It is mentioned the use of polyethylene or polypropylene fibers as an inert transparent uniform supporting substrate.
In the U. S. Pat. No. 4,442,247 (Ishikura et al) there are described paint compositions containing special types of aqueous resins. As a result of the specific interaction between the two types of resins, stable compositions are obtained which avoid separation of solid material and resin coagulation. Nothing is mentioned in this patent on the optical properties of the resins.
In the U.S. Pat. No. 4,684,675 (Collier), it is described a matte paint film in the visible range, produced by incorporation of polyolefins in general, which include polyethylene, polypropylene, polybutene and polypentene particles.
It is an object of the present invention to provide new compositions posessing film forming properties comprising specific filler additives possessing high reflectance in the thermal infra-red wavelengths. It is another object of the present invention to provide new compositions possessing film forming properties wherein said filler additives decrease the gloss appearance at visible light.